A pressure-sensitive adhesive tape is essentially a pressure-sensitive adhesive coated on a flexible substrate backing. The tapes are usually stored in rolls in which each successive adhesive layer is in contact with the backing of the underlying layer. If the adhesive is a tackified block copolymer and there is too much adhesion between the adhesive layer and the backing, when the tape is unrolled for use the adhesive layer may stick to the backing and delaminate or separate from the adhesive side of the tape.
To prevent such delamination, and for ease of unwinding, the non-adhesive side of the tape i.e., the flexible substrate backing, is usually coated with a low adhesion backsize. A low adhesion backsize needs a balance of various properties to be effective. It should have flexibility and strength. The low adhesion backsize should adhere to, and form an even film on, the backing for even distribution of releasability. It should not contaminate the pressure-sensitive adhesive.
Polyurethanes that are known to be suitable for use as low adhesion backsize and inherently possess releasability have generally been soluble only in organic solvents. Since the low adhesion backsize is applied from solution, the use of organic solvent is necessitated, and after the low adhesion backsize has been applied to the tape backing the organic solvent must be removed and disposed of. Environmental considerations have led to a search for water-soluble, water-dispersible or water-borne compounds suitable for use as low adhesion backsize to eliminate or reduce the need for organic solvents.